Constant Internal Energy Process

A tank having a volume of 0.1 m3 contains air at 14 MPa and 50oC. It is connected through a valve to a larger tank having a volume of 15 m3, which is completely evacuated. The entire assembly is completely insulated. The valve is opened and the gas allowed to come to equilibrium in both tanks. Calculate the final pressure.

Calculations:

For this process, Q = 0 and W = 0. Therefore, DU = 0.

DU = mCvDT = 0.

Therefore, DT = 0.

For an ideal gas, PV = nRT

Since T is constant, P1V1 = P2V2

14 x 0.1 = P2 x (0.1 + 15)

i.e., final pressure

P2 = 92.715 KPa.